Monroe Township is a township in southern Middlesex County, in New Jersey, United States. It is part of the outer-ring suburbs of the New York metropolitan area. The township is also centrally located within the Raritan Valley region. As of the 2020 United States Census, the township's population was 48,594, reflecting an increase of 9,462 (+24.2%) from the 39,132 counted in the 2010 Census.